1. Field of the Invention
The present invention relates generally to the field of gear reducers, such as machines designed with one or multiple reduction stages within a support housing. More particularly, the invention relates to novel features of a gear reducer support housing which facilitate its manufacture and assembly in the final gear reducer product.
2. Description of the Related Art
Gear reducers of various types are ubiquitous in the field of industrial mechanical power transmission. Such gear reducers are typically employed to reduce the speed of a rotational input shaft to a desired level, and to, consequently, increase the torque applied to a load. Many different designs for such products have been proposed and are presently in use. In one particular type of gear reducer, sometimes referred to as a torque arm, one or more gear reduction stages are formed in a housing which may be supported on a machine surface, or which may be supported directly on an input or output shaft as an overhung load. To provide the range of gear reduction combinations and torque and speed ratings needed by systems design engineers, manufacturers typically offer a range of similar products through a product family, varying in each both the rating of the various components, the overall gear reduction ratio, the torque characteristics, mounting configurations, and so forth.
Gear reducers of the type described above may be configured as single or multiple-stage machines. In general, the overall gear reduction ratio of the machine is defined by the parameters of input pinions or gears, intermediate pinions and gears, and output gearing. In a single-stage reducer, the gear reduction ratio is defined by the configuration of the input pinion and output gear which intermesh with one another. In multiple-stage machines, the overall gear reduction is the product of the individual reduction ratios of the successive stages.
Gear reducers of the type described above require a number of components which are separately manufactured, machined, and finally assembled into the packaged product. In general, the various components include the pinions and gearing of the rotating assemblies, the shafts or hubs of the rotating assemblies, support bearings for holding the rotating assemblies in the support housing, the various support housing elements, and seal assemblies positioned between the rotating assemblies and the support housing where the shafts or hubs extend from the housing. Depending upon the gear reducer design, size and rating, the support housing may be one of the more complex and costly items. In particular, gear reducer housings are often made of sturdy castings, such as steel alloy castings, which must be machined to receive the rotating assemblies, bearings, and so forth. Moreover, the support housings must be machined in a number of steps, to define the various sealing surfaces, aligned support surfaces, and the features used to assemble the gear reducer and maintain a unified structure as defined by the housing itself.
Conventional gear reducer designs have generally not provided for significantly reduced or optimized manufacturing and assembly. For example, housings of gear reducers designed as shells to receive the rotating groups often begin as a casting which must be machined in a number of sequential manufacturing steps and fixtures. Flat sealing and locating surfaces are generally machined, such as in a milling or grinding operation, followed by refixturing of the housing blank for machining of bearing support surfaces, sealing surfaces for rotating assemblies, and so forth. In many instances, additional holes are bored for bolts or similar fasteners used to maintain the housing components in the assembled unit. The resulting machining operations can be quite extensive and costly, often representing one of the more substantial costs in the manufacturing of the product.
There is substantial need, therefore, for improved techniques for manufacturing and assembling gear reducers and similar products. There is a particular need for a technique which can reduce fixturing and machining costs and steps, by judiciously forming features of the gear reducer housing.
The present invention provides novel features of a gear reducer housing designed to respond to these needs. The features facilitate manufacturing of the housing sealing and support surfaces, as well as the final assembly of the housing components in the product. The features may be employed in any suitable gear reducer housing design, but are particularly well suited to housings in which a peripheral flange, partial or complete, extends around at least a portion of the housing shell. The invention is also particularly well suited to housings in which mating housing components have fastener sets which extend through such partial or complete flanges for assembly.
In a presently preferred configuration, the gear reducer housing includes a plurality of fixturing pads which support the housing during machining operations. The fixturing pads may be formed on the housing blank following casting, but are conveniently formed as reduced thickness regions of a flange during the casting process. Thus, with no further machining, the housing blank may be fixtured a single time by retaining the housing at the fixturing pads, and a series of machining processes may be performed on the blank without refixturing. Other features may similarly be formed in the blank, or may be machined in subsequent operations. For example, slotted apertures are formed, preferably during the casting of the housing blank, at mirror-image locations about a centerline of the housing blank. Similar slotted apertures are formed on a mating housing component. The housing components, following machining and assembly with the gear reducer rotating assemblies, may then be secured to one another via the slotted apertures, axis of which are transverse to one another, providing inherent tolerance in the location of fastener sets used to secure the components in the assembly. Other similar features may be formed in the housing to further facilitate machining and assembly.